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Is stainless steel magnetic? Magnetic properties of high-quality austenitic stainless steels 12x18n10t magnetic properties.

Given the fact that stainless steel is now available in a wide variety of grades, it is impossible to unequivocally answer the question of whether it is magnetized or not. The magnetic properties depend on the chemical composition and, accordingly, on the internal structure of the alloys.

A portable metal analyzer allows you to quickly determine the content of chemical elements and draw a conclusion about the quality of stainless steel

What determines the magnetic properties of materials

A magnetic field with a certain level of its intensity (H) acts on the bodies placed in it in such a way that it magnetizes them. In this case, the intensity of such magnetization, which is denoted by the letter J, is directly proportional to the field strength. The formula that calculates the magnetization intensity of a certain substance (J = ϞH) also takes into account the proportionality factor Ϟ - the magnetic susceptibility of the substance.

Depending on the value of this coefficient, all materials can be included in one of three categories:

paramagnets - the coefficient Ϟ is greater than zero;
diamagnets – Ϟ zero;
ferromagnets - substances whose magnetic susceptibility is significant (such substances, which, in particular, include iron, cobalt, nickel and cadmium, are able to actively magnetize, even when placed in weak magnetic fields).

The magnetic properties that stainless steel possesses are also related to its internal structure, which may include austenite, ferrite and martensite, as well as combinations of them. At the same time, the magnetic properties of stainless steel are influenced by both the phase components themselves and the ratio in which they are in the internal structure.

Stainless steels with good magnetic properties

Stainless steel has good magnetic properties, in which the following phase components predominate:

Martensite is a pure ferromagnet.
Ferrite - this phase component of the internal structure of stainless steel, depending on the heating temperature, can take two forms. Such a structural form becomes a ferromagnet if the steel is heated to a temperature below the Curie point. If the heating temperature of the stainless steel is above this point, then high-temperature delta ferrite, which is a pronounced paramagnet, begins to predominate in the alloy.

From the foregoing, we can conclude that the stainless steel is magnetized, in the internal structure of which martensite predominates. Like conventional carbon steels, these alloys react to a magnet. On this basis, they can be distinguished from non-magnetic.

Steel grade 30X13 is less ductile than alloy 20X13, despite a similar composition (click to enlarge)

This category also includes an alloy of the 20X17H2 brand, which is characterized by a high content of chromium in its chemical composition, which significantly enhances its corrosion resistance. Why is this stainless steel popular? The fact is that, in addition to high resistance to corrosion, it is characterized by excellent workability using cold and hot stamping, cutting methods. In addition, products made from such material are well welded.

ferritic

A common ferritic type magnetic steel, which, due to the low carbon content in its chemical composition, is more soft than martensitic alloys, is 08X13, which is actively used in food production. Products and equipment intended for washing, sorting, grinding, sorting, as well as transporting food raw materials are made from such stainless steel.

Martensitic-ferritic

A popular brand of magnetic stainless steel, the internal structure of which consists of martensite and free ferrite, is 12X13.

Corrosion resistance of steel grade 12X13 (another name is 1X13)

Stainless steels that do not have magnetic properties

Stainless steels that are not magnetic include chromium-nickel and chromium-manganese-nickel. They are usually divided into several groups.

Austenitic

The most popular brand of such stainless steels, which occupy a leading position among non-magnetic steel alloys, is 08X18H10 (an international analogue according to AISI 304 classification). Steels of this type, which also include 08X18H10, 08X18H10T, 12X18H10T, 10X17H13M2T, are actively used in the manufacture of equipment for Food Industry; kitchen utensils and cutlery; sanitary equipment; containers for food liquids; elements of refrigeration equipment; containers for food products; medical supplies, etc.

The great advantages of such stainless steel, which does not have magnetic properties, are its high corrosion resistance, demonstrated in many aggressive environments, and manufacturability.

Austenitic-ferritic

Steels of this group, the most popular grades of which are 08X22H6T, 08X21H6M2T and 12X21H5T, are distinguished by a high chromium content, as well as a low nickel content. To give such a stainless steel the required characteristics (an optimal combination of high strength and good ductility, resistance to intergranular corrosion and corrosion cracking), elements such as copper, molybdenum, titanium or niobium are introduced into its chemical composition.

Most of our products are made from stainless steel. Without fail, the second bottom of the chimney is made of stainless steel - this part takes on hot smoke from the chimney, so the requirements for anti-corrosion protection are increased here.

Sometimes our customers try to check the quality of stainless steel with a magnet - there is such a "folk way". But do not rush to accuse the supplier of cheating, if you suddenly discovered the magnetic properties of the "stainless steel". In fact, more than 250 grades of steel are now being produced, which has the common name "stainless", but is very different in composition and properties and may well be magnetic.

Modern classification of stainless steel

Stainless steel is a type of alloy steel that resists corrosion due to its chromium content. In the presence of oxygen, chromium oxide is formed, which creates an inert film on the steel surface that protects the entire product from adverse effects.

Not every grade of stainless steel demonstrates the resistance of the chromium oxide film to mechanical and chemical damage. Although the film recovers when exposed to oxygen, special grades of stainless steel have been developed for use in harsh environments.

The first conditional type of grouping:

food
heat resistant steel
acid resistant steel

The second type of classification is by microstructure:

Austenitic- non-magnetic steel with main components of 15-20% chromium and 5-15% nickel which increases corrosion resistance. It is well exposed to heat treatment and welding. It is the austenitic group of steels that is most widely used in industry and in the production of fasteners.
Martensitic (Martensitic)- significantly harder than austetitic steels and can be magnetic. They are hardened by quenching and tempering like simple carbon steels, and are used mainly in the manufacture of cutlery, cutting tools and general engineering. More susceptible to corrosion.
Ferritic (Ferritic) steels are much softer than martensitic steels due to the low carbon content. They also have magnetic properties.

Stainless steel marking

In Russia and the CIS countries, an alphanumeric system has been adopted, according to which the content of steel elements is indicated by numbers, and the name of the elements is indicated by letters. Common to all designations are the letter designations of alloying elements: H - nickel, X - chromium, K - cobalt, M - molybdenum, B - tungsten, T - titanium, D - copper, G - manganese, C - silicon.

Standard stainless steels, according to GOST 5632-72, are marked with letters and numbers (for example, 08X18H10T). In the United States, there are several systems for designating metals and their alloys. This is due to the presence of several standards organizations, these include AMS, ASME, ASTM, AWS, SAE, ACJ, ANSI, AJS. It is quite clear that such marking requires additional clarification and knowledge when trading in metal, placing orders, etc.

Europe (EN)	Germany (DIN)	USA (AISI)	Japan (JIS)	CIS (GOST)









	X6CrNiMoTi17-12-2

Learn more about the grades of stainless steel we use

Stainless steel AISI 430 ( Russian standard 12X17);

Due to the low carbon content - the most plastic, bends relatively easily. The high percentage of chromium provides a high level of protection. Retains its properties in corrosive and sulfur-containing environments, resistant to sudden temperature changes. We use AISI 430 stainless steel for bending strips, decorative items, intake hoods, chimneys (if there is no gas and diesel), external insulation of chimneys on sandwich pipes.

Stainless steel AISI 304 (Russian standard 08X18H10);

This is the most demanded stainless steel, which is in great demand in all industries, including our bending production. It has a high level of corrosion resistance. Our main application of this type of stainless steel is chimneys, diesel and gas penetration, the inner pipe on sandwich pipes for the chimney and in other products that will be used in aggressive environments. AISI 304 stainless steel is chromium-nickel and belongs to the austenitic group of steels, that is, it is not magnetic. As well as its analogues steel 08X18H10, 08X18H10T, 12X18H10T, etc.

However, under certain physical influences, metal products of this group can exhibit magnetic properties. So, for example, when welding any type, under the influence high temperature, there is a burnout of alloying elements and a change in the structure of the metal in place weld. Accordingly, in this place the metal begins to exhibit magnetic properties. A change in the structure of the metal crystal lattice also occurs when mechanical action such as metal forging, thread rolling, pressing, metal bending, etc. Which also leads to the manifestation of magnetic properties. At the same time, the general chemical and physical properties steel does not change.

Stainless steel AISI 316 (10X17H13M2);

AISI 316 stainless steel is obtained by adding molybdenum to 304 stainless steel, which further increases corrosion resistance and the ability to retain properties in aggressive acidic environments, as well as at high temperatures. This stainless steel is more expensive than 304, but its use is necessary for products operating at high temperatures (chimneys). It bends badly.

In addition to manufacturing stainless steel materials, we also sell Vulkan chimneys - here, too, everything is not easy when choosing a stainless steel grade. For example, for the manufacture of linear pipes and fittings (tees, bends, brackets, etc.), high-alloy austenitic stainless steels are used, specially designed for use in aggressive environments. The inner contour of the chimney elements is made of AISI 321 steel, which has increased heat resistance (up to 850 ° C), mechanical and chemical strength. The outer contour is made of austenitic polished AISI 304 stainless steel. Due to the increased proportion of nickel in its formula, AISI 304 steel is deeply austenitic - that is, it is structurally stable and not prone to intergranular corrosion. In addition, steel is resistant to environment, temperature changes, can be used in any climatic conditions.

Magnetic - non-magnetic stainless steel depends on the nickel content in its composition. Classic stainless steel - 12x18n10t, it contains ten percent nickel. If the percentage of nickel is reduced to 9 and below, then the stainless steel begins to magnetize, even if it is stainless steel of the austenitic class. For example 06X22H6T. It is only 6 percent. nickel - it is magnetic. And its structure does not consist of pure austenite, but of a mixture of austenite with ferrite (which is magnetite). But still, there is little theory - when chromium is added to iron, then after 12 ... 13 percent of chromium, the corrosion resistance of the alloy increases sharply, abruptly. That is, at 10 percent chromium, the corrosion resistance is still low, and at 13 percent, it is an order of magnitude higher. And no matter what structure the steel has (even austenite, even ferrite, even martensite). It would seem - the more chromium the better? No.

plasticity (for bending a complex profile)
weldability
corrosion resistance at high temperatures

GOST		magnetism	Characteristics	Application examples
08X18H10	304		Low carbon steel, austenitic non-hardenable, corrosion resistant, non-magnetic under low magnetization conditions (if cold worked). Easy to weld, resistant to intercrystalline corrosion. High strength at low temperatures. Can be electro-polished.	Installations for the food, chemical, textile, oil, pharmaceutical, paper industries. We use in the manufacture of chimneys, diesel and gas penetrations, internal pipes on sandwich pipes for a chimney and in other products that will be used in aggressive places.
08X18H10			Austenitic steel, not hardenable, especially suitable for welded structures. Highly resistant to intercrystalline corrosion, used at temperatures up to 425°С. By chemical composition differs from 304 by almost half the carbon content.	It finds the same applications as AISI 304 in fabrication of welded structures and in industries where resistance to intergranular corrosion is required.
08Х17Н13М2			The steel is austenitic, not hardenable, and the presence of molybdenum (Mo) makes it particularly resistant to corrosion. Also, the technical properties of this steel at high temperatures are much better than those of similar steels that do not contain molybdenum.	Chemical equipment exposed to particularly severe conditions, tools that come into contact with sea water and the atmosphere, film developing equipment, boiler bodies, food processing plants, waste oil containers for coking plants.
03Х17Н14М2			Steel similar to AISI 316, austenitic non-hardenable, with very low carbon C content, especially suitable for fabrication of welded structures. It has high resistance to intergranular corrosion, it is used at temperatures up to 450°С. In chemical composition, it differs from 316 by almost half the carbon content.	It finds the same applications as AISI 316 in welded structures where high corrosion resistance is required. Particularly suitable for the production of food products and ingredients (mayonnaise, chocolate, etc.)
10X17H13M2T			The presence of titanium (Ti), five times the content of carbon C, provides a stabilizing effect in relation to the deposition of chromium (Cr) carbides on the surface of the crystals. Titanium (Ti) indeed forms carbides with carbon, which are well distributed and stabilized inside the crystal. Possesses the increased resistance to intercrystalline corrosion.	Parts with increased resistance to high temperatures and environments with the presence of new chlorine ions. Blades for gas turbines, cylinders, welded structures, collectors. Used in the food and chemical industries.
08X18H10T			Titanium (Ti) chromium-nickel steel, austenitic, non-hardenable, non-magnetic, especially recommended for fabrication of welded structures and for use at temperatures between 400°C and 800°C, corrosion resistant.	Discharge manifolds for aircraft engines, boiler casings or annular manifolds for petrochemical equipment. Compensation connections. Chemical equipment and equipment resistant to high temperatures.
		+	Basic chromium ferritic steel with improved deep drawing ability, not hardenable. 18%Cr. Magnitite!	Everyday goods, kitchen equipment, decor, finishes, brass annealing containers, naphtha burners, nitric acid tanks and tanks. We use for bending strips, decorative products, intake hoods, chimneys (if there is no gas and diesel), external insulation of chimneys on sandwich pipes.

Brief chart of stainless steel grades (AISI classification)

Depending on the purpose, working conditions, aggressiveness of the environment, the products are subjected to: a) hardening (austenization); b) stabilizing annealing; c) stress relief annealing; d) step processing. Products are hardened in order to: a) prevent the tendency to intergranular corrosion (products operate at temperatures up to 350 ° C); b) improve resistance to general corrosion; c) eliminate the revealed tendency to intergranular corrosion; d) prevent the tendency to knife corrosion (welded products work in nitric acid solutions); e) eliminate residual stresses (products of a simple configuration); e) increase the plasticity of the material. Hardening of products must be carried out according to the regime: heating up to 1050-1100 ° C, parts with a material thickness of up to 10 mm should be cooled in air, over 10 mm - in water. Welded products of complex configuration in order to avoid the leash should be cooled in air. Holding time during heating for hardening for products with a wall thickness of up to 10 mm - 30 min, over 10 mm - 20 min + 1 min per 1 mm of maximum thickness. When quenching products intended for operation in nitric acid, the heating temperature for quenching must be kept at the upper limit (while the exposure of welded products must be at least 1 hour). Stabilizing annealing is used to: a) prevent susceptibility to intergranular corrosion (products operate at temperatures above 350 °C); b) removal of internal stresses; c) elimination of the detected tendency to intergranular corrosion, if for some reason hardening is not advisable. Stabilizing annealing is acceptable for products and welded joints from steels in which the ratio of titanium to carbon is more than 5 or niobium to carbon is more than 8. Stabilizing annealing to prevent the tendency to intergranular corrosion of products operating at temperatures above 350 ° C can be subjected to steel containing no more than 0.08% carbon. Stabilizing annealing should be carried out according to the regime: heating to 870-900 °C, holding for 2-3 hours, cooling - in air. During heat treatment of large-sized welded products, it is allowed to carry out local stabilizing annealing of the closing welds according to the same regime, while all welded elements must be subjected to stabilizing annealing before welding. When carrying out local stabilizing annealing, it is necessary to ensure simultaneous heating and cooling along the entire length of the weld and adjacent zones of the base metal to a width equal to two or three weld widths, but not more than 200 mm. Manual heating is not allowed. For a more complete removal of residual stresses, annealing of products from stabilized chromium-nickel steels is carried out according to the following regime: heating to 870-900 ° C; holding for 2-3 hours, cooling with an oven to 300 °C (cooling rate 50-100 °C/h), then in air. Annealing is carried out for products and welded joints made of steel, in which the ratio of titanium to carbon is more than 5 or niobium to carbon is more than 8. Step processing is carried out to: a) relieve residual stresses and prevent a tendency to intergranular corrosion; b) to prevent the tendency to intergranular corrosion of welded joints of complex configuration with sharp transitions in thickness; c) products with a tendency to intergranular corrosion, which cannot be eliminated by another method (hardening or stabilizing annealing). Step processing must be carried out according to the mode: heating up to 1050-1100 ° C; holding time during heating for hardening for products with wall thickness up to 10 mm - 30 min, over 10 mm - 20 min + 1 min per 1 mm of maximum thickness; cooling with the maximum possible speed up to 870-900°C; exposure at 870-900 °C for 2-3 hours; cooling with a furnace up to 300 °C (speed - 50-100 °C/h), then in air. To speed up the process, stepwise processing is recommended to be carried out in two-chamber or two furnaces heated to different temperatures. When transferring from one furnace to another, the temperature of the products should not be lower than 900 °C. Step processing is allowed for products and welded joints made of steel, in which the ratio of titanium to carbon is more than 5 or niobium to carbon is more than 8.

Good day, dear distillers! We recently encountered a surprising phenomenon for us. Some parts of equipment made of AISI 304 stainless steel are magnetic and rust. Which surprised us a lot. Accordingly, we decided to look into this issue in more detail and this is what we found out.

AISI 304 stainless steel is chromium-nickel and belongs to the austenitic group of steels, that is, it is not magnetic. As well as its analogues steel 08X18H10, 08X18H10T, 12X18H10T, etc.

However, under certain physical influences, metal products of this group can exhibit magnetic properties. So, for example, during welding of any type, under the influence of high temperature, the alloying elements burn out and the structure of the metal changes in the place of the weld. Accordingly, in this place the metal begins to exhibit magnetic properties. A change in the structure of the crystal lattice of a metal also occurs under mechanical action, such as metal forging, thread rolling, pressing, metal bending, etc. Which also leads to the manifestation of magnetic properties. At the same time, the general chemical and physical properties of steel do not change.

Now for the rust. First of all, rust can appear on the weld. What might cause this to happen. In the process of welding, a film is formed on the surface of the seam, which has low resistance to an aggressive environment, so it can become covered with corrosion, that is, rust. Also, rust can appear in small spots on the metal itself. This is due to the way the metal is processed, so to speak, beauty guidance. After welding, the structure is cleaned with a steel brush, so-called risks are induced. The microparticles from this brush get stuck in a softer stainless steel, they then appear as rusty spots when interacting with moisture contained, including in the air. Both of these types of corrosion are simply removed with a polishing sponge and no longer appear.

In general, in the process of studying these issues, we realized one thing, physics is an interesting and fascinating science that will surprise us more than once!

Sincerely, NOVATRA store team!

Information taken from scientific sources.

Many private consumers are concerned about the question of whether stainless steel is magnetized or not. The fact is that it is impossible to visually distinguish ordinary steel from stainless steel, and therefore the method of checking the material with a magnet is widespread. It is believed that stainless steel should not be magnetized, but in practice this diagnostic method does not always allow you to get a reliable result. As a result, often materials that do not magnetize perfectly tolerate contact with water. On the other hand, products that have passed the "test" become rusty. As a result, the question of whether or not stainless steel is magnetized becomes more and more confusing. What determines the magnetic properties of stainless steel?

The term "stainless steel" means various materials, the composition of which may contain ferrite, martensite or austenite in its structure, as well as their various combinations. The characteristics of stainless steel depend on the phase components and their ratio. So which stainless steel is magnetic and which is not?

Stainless steels that are not magnetic

Most often for the production of stainless steel is used chromium-nickel or chromium-manganese-nickel alloy. These materials are non-magnetic. They are extremely widespread, which is why many consumers, based on their practical experience give a negative answer to the question of whether stainless steel is magnetized. Non-magnetic steels are divided into the following groups:

· Austenitic. Austenitic class materials (for example, AISI 304 steel) are used to produce equipment for the food industry, containers for food liquids, kitchen utensils, as well as a variety of refrigeration, marine and sanitary equipment. High resistance to aggressive environments provides a wide distribution of this type of steel.

· Austenitic-ferritic. These materials are based on chromium and nickel. Titanium, molybdenum, copper and niobium can be used as additional alloying elements. The main advantages of austenitic-ferritic steels include improved strength and greater resistance of the structure to stress corrosion cracking.

Stainless steels that are magnetic

To determine why a stainless steel is magnetized, it is enough to familiarize yourself with the phase components of magnetic materials. The fact is that martensite and ferrites are strong ferromagnets. Corrosion is not terrible for such materials, but at the same time the magnet acts on them, as well as on ordinary carbon steel. The presented group of stainless steel includes chromium or chromium-nickel steels of the following groups:

· Martensitic. Thanks to quenching and tempering, the material is characterized by high strength, which is not inferior to the corresponding parameter of standard carbon steels. Martensitic grades find their application in the manufacture of abrasives and in the engineering industry. Cutlery is also made of them, and in this case, you can safely give a positive answer to the question of whether food grade stainless steel is magnetized. Materials of classes 20X13, 30X13, 40X13 are widely used in a ground or polished state, and class 20X17H2 is highly valued for its unsurpassed resistance to corrosion, surpassing even 13% chromium steels in this indicator. Due to its high processability, this material is well suited for all types of processing, including stamping, cutting and welding.

· ferritic. This group of materials is lighter than martensitic steels due to the lower carbon content. One of the most sought-after alloys is AISI 430 magnetic steel, which finds its application in the manufacture of equipment for food production plants.

The practical significance of the magnetic properties of stainless steel

The magnetic properties of stainless steel do not affect its performance in any way. There is no technical possibility to determine the corrosion resistance of the material at home. Of course, it would be convenient to have such a convenient and simple indicator as a magnet, so that with its help it is possible to accurately determine the quality of the material by a simple check. But the fact is that there is simply no unequivocal answer to the question whether 18/10 stainless steel is magnetized or not. The only way protect yourself from fakes - purchase dishes and other stainless steel products from reliable suppliers.